var app = new Vue({
    el: "#app",
    data: {
        // name: "莫娜",
        scrollTop: 0,
        list: [
            "莫娜",
            "角色介绍",
            "背景故事",
            "关于作者"
        ],
    },

    mounted: function () {
        window.addEventListener('scroll', this.scrollToTop);
    },
    destroyed: function () {
        window.removeEventListener('scroll', this.scrollToTop);
    },


    methods: {
        // 点击图片回到顶部方法，加计时器是为了过渡顺滑
        backTop() {
            const that = this;
            let timer = setInterval(() => {
                let ispeed = Math.floor(-that.scrollTop / 5);
                document.documentElement.scrollTop = document.body.scrollTop = that.scrollTop + ispeed;
                if (that.scrollTop === 0) {
                    clearInterval(timer);
                }
            }, 16)
        },

        // 为了计算距离顶部的高度，当高度大于60显示回顶部图标，小于60则隐藏
        scrollToTop() {
            const that = this;
            let scrollTop = window.pageYOffset || document.documentElement.scrollTop || document.body.scrollTop;
            that.scrollTop = scrollTop;
            if (that.scrollTop > 60) {
                that.btnFlag = true;
            } else {
                that.btnFlag = false;
            }
        },
    }
});

